Incidence of the Enterococcal Surface Protein (esp) Gene in Human and Animal Fecal Sources

Abstract

The occurrence of the enterococcal surface protein (esp) gene in the opportunistic pathogens Enterococcus faecalis and E. faecium is well-documented in clinical research. Recently, the esp gene has been proposed as a marker of human pollution in environmental waters; however, information on its relative incidence in various human and animal fecal sources is limited. We have determined the occurrence of the esp gene in enterococci from human (n=64) and animal (n=233) fecal samples by polymerase chain reaction using two primer sets: one presumably specific for E. faecium (esp(fm)) and the other for both E. faecalis and E. faecium (esp(fs/fm)). We believe that this research is the first to explore the use of esp(fs/fm) for the detection of human waste in natural environmental settings. The incidence in human sources was 93.1% esp(fm) and 100% esp(fs/fm) in raw sewage influent; 30% for both esp(fm) and esp(fs/fm) in septic waste; and 0% esp(fm) and 80% esp(fs/fm) in active pit toilets. The overall occurrence of the gene in animal feces was 7.7% (esp(fs/fm)) and 4.7% (esp(fm)); animal types with positive results included dogs (9/43, all esp(fm)), gulls (10/34, esp(fs/fm); 2/34, esp(fm)), mice (3/22, all esp(fs/fm)), and songbirds (5/55, all esp(fs/fm)). The esp gene was not detected in cat (0/34), deer (0/4), goose (0/18), or raccoon (0/23) feces. The inconsistent occurrence, especially in septic and pit toilet sewage, suggests a low statistical power of discrimination between animal and human sources, which means a large number of replicates should be collected. Both esp(fm) and esp(fs/fm) were common in raw sewage, but neither one efficiently differentiated between animal and other human sources.